бэк 3

def funk(expr):
import re
token_list = re.split("([^0-9])", expr)
print(token_list)
stack = [0]
for token in token_list:
if token == '' or token == ' ':
continue
if token == "-":
minus = stack.pop() - stack.pop()
stack.append(minus)
elif token == "/":
delenie = stack.pop() / stack.pop()
stack.append(delenie)
elif token == '+':
sum = stack.pop() + stack.pop()
stack.append(sum)
elif token == '*':
product = stack.pop() * stack.pop()
stack.append(product)
else:
stack.append(int(token))
return stack.pop()


n = funk("5 6 - 2 *")
print(n)